Eur. Phys. J. B 27, 449-458 (2002)
https://doi.org/10.1140/epjb/e2002-00177-x

Optical functions of InGaP/GaAs epitaxial layers from 0.01 to 5.5 eV

¹ INFM-Dipartimento di Fisica “A. Volta” dell'Università, Via Bassi 6, 27100 Pavia, Italy
² INFM-Dipartimento di Fisica dell'Università, Viale delle Scienze, 43100 Parma, Italy

Corresponding author: ^a guizzetti@fisav.unipv.it

Received: 13 December 2001
Published online: 25 June 2002

Abstract

In_0.49Ga_0.51P films, both undoped and doped n- and p-type (up to 10¹⁸ cm^-3), were grown lattice matched on GaAs substrates, with different miscut angles, by Metal-Organic Vapour Phase Epitaxy (MOVPE) at different temperatures. The shift of the fundamental gap E₀, caused by “ordering effect” was measured as a function of temperature by photoluminescence. The complex refractive index and the dielectric function at room temperature were determined from 0.01 to 5.5 eV by using complementary data from fast-Fourier-transform far-infrared (FFT-FIR), dispersive, and ellipsometric spectroscopies. The effect of the native oxide was accounted for and the self-consistency of the optical functions was checked in the framework of the Kramers-Kronig causality relations. In the restrahlen region the dielectric function was well fitted by classical Lorentz oscillators; in the transparent region below E₀, the refractive index was modelled by a Sellmeier dispersion relation; in the interband region the dielectric function was well reproduced by analytical lineshapes associated to seven critical points. Thus parametrized analytical expressions were obtained for the optical functions all over the spectral range, without discontinuities, to be used in the modelling and characterization of multi-layer structures, also on opaque substrates.